Electrical appliances such as automatic dishwashers have long been known in the art. Automatic dishwashers are a particularly convenient and efficient way to clean dishes following their use. Such dishwashers generally include a tub for holding the dishes and one or more streams of pressurized fluid for washing food and drink residue from the dishes.
The dishwashing process generates a considerable amount of noise. Consumers have shown a preference for dishwashers that provide more quiet operation. In order to address this preference, manufacturers of dishwashers have insulated dishwashers in various ways in an attempt to suppress noise.
One method of noise suppression commonly used today is to apply a mass dampener material such as bitumen and/or mastic to the outside of the tub. A mass dampener material such as mastic can greatly reduce wash noise in the 35-60 Hz range.
The use of mass dampener materials of this type does, however, result in a number of drawbacks. More specifically, the mastic undergoes a bake-on process in order to adhere the mastic to the tub which is usually constructed from stainless steel. This bake-on process often creates variations in the stiffness of the tub thereby resulting in acoustic variations from unit to unit of anywhere up to plus or minus 1.5 Db.
Further, while the mastic is effective in suppressing wash noise in the 35-60 Hz range it does little to suppress pump motor noise at or around 125 Hz-about 400 Hz range. In fact, the application of mastic to the tub can actually cause the tub to “ring” at the motor frequency thereby accentuating motor noise. Furthermore, the mastic may harden over time, and may become less effective as the appliance ages.
The present invention relates to an insulation element and method of insulating an electrical appliance such as a dishwasher that allows one to reduce or eliminate the use of mass dampener materials such as mastic while still effectively suppressing the noise generated during the washing operation. The reduction or elimination of mastic from the side of the tub significantly reduces acoustic variation from unit to unit thereby allowing engineers to produce a more effective noise insulation system for all units. Further, as an added bonus, the present invention also allows the electrical appliance to operate at higher energy efficiency.